Pathology of Left Ventricular Outflow Tract Obstruction

Lesions causing obstruction to the outflow of blood from the left ventricle may reside in the ascending aorta, the aortic valve, or the outflow tract of the left ventricle. Conditions involving the ascending aorta are usually congenital, and designated as supravalvular aortic stenosis. A tendency is present for this condition to be associated with mental retardation, stenosis of peripheral pulmonary arteries, stenosis of branches of the aortic arch, and a peculiar facies. Secondary narrowing of coronary arteries may occur. Obstruction at the aortic valve is usually represented by a stenotic lesion. In some instances, the basis for stenosis is congenital; in others, it is acquired either through the direct effects of rheumatic endocarditis or through calcification of an acquired or congenital bicuspid aortic valve. Atresia of the aortic valve causes death in infancy. Subaortic stenosis is a complicated subject. It may be represented by a primary anomaly of the left ventricular outflow tract or may be secondary either to conditions primary in the mitral valve or to generalized diseases of the myocardium. In some instances of subaortic stenosis, this process is one part of a complex cardiac malformation.